Molybdenum-mediated imido-transfer reaction of N-sulfinylamines with dimethylformamide

Article abstract of DOI:10.1016/j.mencom.2009.05.019

Dimethylformamide undergoes molybdenum-mediated metathetical imido-deoxygenation with ortho-substituted by donor atoms N-sulfinylanilines affording formamidines; N-sulfinylamines undergo molybdenum-mediated condensation into sulfurdiimines.

Full text of DOI:10.1016/j.mencom.2009.05.019

Mendeleev
Communications
Mendeleev Commun., 2009, 19, 165–166
Molybdenum-mediated imido-transfer reaction
of N-sulfinylamines with dimethylformamide
Anton A. Zhizhin, Dmitry N. Zarubin* and Nikolai A. Ustynyuk
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5085; e-mail: zaroubine@ineos.ac.ru
DOI: 10.1016/j.mencom.2009.05.019
Dimethylformamide undergoes molybdenum-mediated metathetical imido-deoxygenation with ortho-substituted by donor atoms
N-sulfinylanilines affording formamidines; N-sulfinylamines undergo molybdenum-mediated condensation into sulfurdiimines.
The metathesis of multiple carbon–carbon bonds is a powerful
tool of fine organic synthesis.1 Examples of transition-metal-
mediated metathesis of carbon–heteroatom or heteroatom–
heteroatom double bonds (heterometathesis) are still rare. In
particular, metathesis of azomethines,2 carbodiimides3 and
diphosphenes,4 metathetical imido-deoxygenation of aldehydes
with isocyanates5 and N-sulfinylamines6 affording imines,
condensation of isocyanates into carbodiimides7 have been
reported. Among these processes, imido-transfer reactions are
of interest because derivatives including an imino (imido) moiety
are important organic compounds.
N-Sulfinylamines R–NSO undergo heterometathesis with
aldehydes, ketones and ketoacid esters to give imines; however,
the scope of reactive substrates is limited by only polyfluorinated
compounds.8 Recently, we have considerably extended the range
of both N-sulfinylamines and aldehydes6 by using vanadium
and molybdenum oxochlorides or imidomolybdenum aroxides
as catalysts in this reaction. Here, we report that carboxylic acid
amides such as dimethylformamide (DMF) can also undergo
metathetical imido-deoxygenation reaction with N-sulfinylamines
mediated by molybdenum diimido dialkyl complex (MesN)2-
Mo(CH2CMe2Ph)2 (Mes = 2,4,6-Me3C6H2) 1.†
Table 1 Reaction of N-sulfinylamines ArNSO with DMF.
O
O
S
1 (3 mol%)
N
N
+
+
N
N
Ar
S
Ar
N
n-heptane, Δ
– SO2
N
Ar
Ar
2
3
Yield of
Yield of
Entry Ar
t/h
formamidine (%) sulfurdiimine (%)
1
2
3
4
5
6
2,4,6-Cl3C6H2
2-CF3C6H4
2-FC6H4
2-MeOC6H4
4-MeOC6H4
2,4,6-Me3C6H2
5
5
2a
2b 78 (73)
44
71a (53b)
3a
3b
3c
9
9
20 2c
43
20 2d 53
no reaction
no reaction
3d 25
aSpectroscopically estimated. bIsolated.
evolution affording formamidines 2a–d in good to moderate yields
(Table 1).‡ The reaction is also catalysed by other molybdenum
diimido dialkyl complexes, in particular, (MesN)2MoR2 (R =
= CH2SiMe3, CH2CMe3), whereas no reaction was observed in
the absence of catalyst. Interestingly, only N-sulfinylanilines
bearing o-substituents with donor atoms (Table 1, entries 1–4)
react with DMF but o-alkylated or o-unsubstituted compounds,
for example, N-sulfinylmesitylamine and 4-methoxy-N-sulfinyl-
aniline (Table 1, entries 5 and 6), are nonreactive. Apart from
formamidines, sulfurdiimines 3a–d formed as by-products in
all cases (Table 1). This fact points out that the alternative
oxo–imido exchange process occurs, in which N-sulfinylamines
react simultaneously as both imidating agents and oxo-con-
taining components. Indeed, under the same conditions in the
absence of DMF, the condensation of N-sulfinylamines proceeds
and results in sulfurdiimines (Table 2).§ As mentioned above,
only o-substituted by donor atoms N-sulfinylanilines are reactive.
The reaction of N-sulfinylamines with DMF occurs in the
presence of imide 1 (3 mol%) in boiling n-heptane with SO2
†
All manipulations were carried out under an argon atmosphere using
standard Schlenk line technique. The 1H and 13C NMR spectra of 1 were
recorded on a Bruker Avance-400 spectrometer (400.13 and 100.61 MHz,
respectively) in C6D6. The 1H and 19F NMR spectra of 2a–d and 3a–d were
recorded on a Bruker Avance 300 spectrometer (300.13 and 282.4 MHz,
respectively) in CDCl3. The residual solvent 1H or 13C resonances were
used as internal references. The 19F NMR spectra were referenced externally
to TFA. Infrared spectra were measured on a Specord M80 spectrophoto-
meter (CHCl3). Mass spectra were measured on a Finnigan POLARIS Q
(EI at 70 eV).
‡
Preparation of (MesN)2Mo(CH2CMe2Ph)2 1. A solution of neophyl
magnesium chloride in Et2O (1.76 mol dm–3, 3.3 ml, 5.8 mmol) was
added dropwise to a stirred suspension of (MesN)2MoCl2(dme) (1.51 g,
2.9 mmol) in Et2O (120 ml) at –78 °C. The reaction mixture was allowed
to warm to ambient temperature and stirred for 12 h. The resulting
orange-red solution was filtered, concentrated in a vacuum to ~50 ml
and cooled to –24 °C to afford analytically pure product as a yellow
crystalline solid, which was filtered off and dried in a vacuum. The yield
was 1.51 g (83%). 1H NMR, d: 7.43 (d, 4H, HPh, J 7.56 Hz), 7.21–7.17
(m, 4H, HPh), 7.08 (t, 2H, HPh, J 7.33 Hz), 6.68 (s, 4H, HMes), 2.17 (s,
12H, o-Me), 2.08 (s, 6H, p-Me), 1.76 (s, 4H, CH2) 1.47 (s, 12H, Me).
13C{1H} NMR, d: 154.61, 150.77, 134.12, 132.15, 128.66, 128.59, 126.67,
126.20, 76.44, 39.66, 32.30, 21.05, 18.83. Found (%): C, 72.42; H, 7.77;
N, 4.45. Calc. for C38H48MoN2 (%): C, 72.59; H, 7.69; N, 4.46.
Reaction of N-sulfinylamines with DMF: general procedure. A 100 ml
Schlenk flask was charged with N-sulfinylamine (3 mmol), DMF (0.22 g,
3 mmol), (MesN)2Mo(CH2CMe2Ph)2 (0.06 g, 0.09 mmol, 3 mol%) as a
catalyst and n-heptane (25–30 ml). The reaction mixture was stirred under
reflux for 5 h for 2a,b and 20 h for 2c,d. The solution was filtered
through a Celite® pad, the solvent was removed at a reduced pressure,
and the residue was crystallised from concentrated solution in n-heptane
at 5 °C (compound 2a) or fractionated in a vacuum (compound 2b).
N,N-Dimethyl-N'-(2,4,6-trichlorophenyl)formamidine 2a: yield 0.4 g
(53%); mp 69–71 °C (lit.,10 70–71 °C). 1H NMR, d: 7.35 (s, CH, 1H), 7.26
(s, 2H, HAr), 3.05 (d, 6H, NMe2). IR (n/cm–1): 1640 (C=N). MS, m/z (%):
250 [M]+ (28), 215 (100), 208 (18), 174 (27).
The spectral data of formamidines 2b–d are given in the Online
Supplementary Materials.
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© 2009 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2009, 19, 165–166
(route B) or N-sulfinylamine (route C) to lead to oxide II and
Table 2 Condensation of N-sulfinylamines ArNSO into sulfurdiimines.
liberate formamidine or sulfurdiimine, respectively. The well-
documented9 imido-deoxygenation of II with N-sulfinylamine
(step D) regenerates complex I.
Thus, we have shown for the first time by the example of
dimethylformamide that carboxylic acid amides undergo meta-
thetical imido-deoxygenation with N-sulfinylamines under media-
tion of molybdenum diimido dialkyl complexes.
O
N
N
N
1 (3 mol%)
Ar
S
Ar
S
Ar
+ SO2
2
n-heptane, Δ
3
Entry Ar
t/h
Yield of sulfurdiimine (%)
1
2
3
4
5
6
2,4,6-Cl3C6H2
2-CF3C6H4
5
7
7
7
3a
3b
3c
3d
72a (62b)
76 (52)
65 (55)
35
2-FC6H4
2-MeOC6H4
4-MeOC6H4
2,4,6-Me3C6H2
This study was supported by the Russian Foundation for
Basic Research (project no. 07-03-00939a).
no reaction
no reaction
aSpectroscopically estimated. bIsolated.
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2009.05.019.
The proposed scheme of the imido-transfer reaction of
N-sulfinylamines with DMF¶ (Scheme 1) includes the initial
step of transimidation of starting complex 1 with N-sulfinylamine
(step A) affording respective arylimide I and N-sulfinylmesityl-
amine.†† Further oxo-deimidation of complex I can proceed
along two competitive routes under the action of either DMF
References
1
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[Mo]=NMes
ArNSO
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MesNSO
3
4
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O
NMe2
NMe2
ArN=S=O
SO2
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ArN=S=NAr
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[Mo]=O
II
7
8
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[Mo] = (MesN)Mo(CH2CMe2Ph)2
Scheme 1
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§
Condensation of N-sulfinylamines: general procedure. A 100 ml
Schlenk flask was charged with N-sulfinylamine (3 mmol), (MesN)2Mo-
(CH2CMe2Ph)2 (0.06 g, 0.09 mmol, 3 mol%) as a catalyst and heptane
(25–30 ml). The reaction mixture was stirred under reflux for 5 h for 3a
and 7 h for 3b–d. The reaction mixture was filtered through a Celite®
pad, the solvent was removed under a reduced pressure, and the residue
was recrystallised from diethyl ether (compounds 3a,d) or fractionated
in a vacuum (compound 3b).
Di(2,4,6-trichlorophenyl)sulfodiimine 3a: orange crystals, yield 0.39 g
(62%); mp 101–102 °C. 1H NMR, d: 7.12 (s, HAr). MS, m/z (%): 420
[M]+ (8), 385 (100), 350 (5), 313 (5), 227 (16), 190 (27), 158 (10), 109
(6). Found (%): C, 34.19; H, 0.89; N, 6.59. Calc. for C12H4Cl6N2S (%):
C, 34.24; H, 0.96; N, 6.65.
9
The spectral data of sulfurdiimines 3b–d are given in the Online
Supplementary Materials.
The reaction mechanism will be published elsewhere.
†† Identified by comparison of spectral data with those of authentic
10 K.-M. Chang and C. O. Knowles, J. Agric. Food Chem., 1977, 25, 493.
¶
1
compound. H NMR, d: 6.91 (s, 2H, HAr), 2.27 (s, 3H, p-Me), 2.23 (s,
3H, o-Me).
Received: 19th December 2008; Com. 08/3253
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